This invention relates generally to sash counter balances in windows, and more particularly to a block and tackle counter balance for windows that reduces the cost of manufacture and installation.
Block and tackle counter balances have been in use in the window industry for many years. The block and tackle device is used to minimize the extension of a spring being used to counter the weight of the window sash. This allowed the balance to be put into a single compact unit.
Heretofore, a number of patents and publications have disclosed aspects of window counter-balances, the relevant portions of which may be briefly summarized as follows:
U.S. Pat. No. 4,089,085 to Fitzgibbon et. al., issued May 16, 1978, discloses the construction and components of a block and tackle sash counter balance.
U.S. Pat. No. 4,811,455 to Ost et al., issued Mar. 14, 1989, teaches a system of anchoring a window balance spring within a channel.
U.S. Pat. No. 4,949,425 to Dodson et al., issued Aug. 21, 1990, discloses the simplified construction of a. window sash balance assembly. The pre-assembled, unitary system includes a spring-loaded block and tackle enclosed within a channel having laterally spaced sidewalls.
Balance Systems, Inc. disclose, in a 1992 brochure, a xe2x80x9c700 Seriesxe2x80x9d block and tackle balance system. Each of said system configurations include a continuous U-shaped channel that encloses the block and tackle and spring assembly.
As depicted in prior art FIG. 13, these balances are typically constructed of a U-shaped rigid body or channel 1020 made of either aluminum or steel, which may be painted or unpainted. A lower pulley housing 1022 generally contains one or more lower pulleys 1024 riveted to the bottom of the rigid channel 1020 and retained within the housing. An upper pulley housing 1026 also contains one or more upper pulleys 1028, and is slidably attached to the lower end of a spring 1030. The upper end of the spring is attached to a rivet 1032 that is fixed at the upper end of the rigid channel 1020, so as to pass through both sides of the channel and to provide a location to which the spring 1030 may be attached (e.g., by a hook at the end of the spring). From the bottom of the channel extends string 1034 with a terminal clip 1036 attached thereto for releasable connection with a sash.
Such prior art balances maintain the spring at an initial tension, which requires that the U-shaped housing be made of a rigid material in such a way as to have significant resistance to a compressive force applied along a longitudinal axis of the channel, so as to avoid collapsing the balance while it is being installed and operated. Accordingly, the rigid U-shaped channel is expensive to manufacture as it requires tooling and equipment for bending the channel and machining it, and the use of a costly metal alloy such as steel or aluminum. For longer and higher weightcarrying counter balances the channel must be constructed of steel for strength. However, steel is subject to corrosion and has to be treated with a corrosion resistant coating (e.g., painted, galvanized). Furthermore, the lower pulley housing 1022 is riveted to the channel 1020, requiring a riveting step at the bottom as well as a rivet for the spring at the top. During manufacture, the riveting steps result in the addition of significant time for assembly, and add to the cost of each balance. The labor involved in the threading of the block and tackle is also very time consuming and can be up to one-third of the cost of the counter balance.
As mentioned earlier the spring (1030) used in the prior art balance is already in the initial stretched or pre-tensioned position when the balance is assembled. This is required to put the spring in its appropriate working range in order to operate the counter balance effectively for the range of weight and size of sash it was designed for. Pre-tensioning of the spring reduces its working range (distance) and does not allow for a use of the spring over its entire working range. Pre-tensioning also forces the length of the balance to be equivalent to that of the sash height, thereby forcing the design to have a longer balance than required for the working range of the sash. Lastly, pre-tensioning also forces the balances to be made in increments (e.g., 1 inch) so as to be able to closely match the sash heights. It also forces the window manufacturer to inventory all. the various size and weight carrying capacities of balances, which can be very expensive.
Finally when the balances are made of a metal such as aluminum alloy or steel, it is often necessary to place a decorative cover on the balances for aesthetic and/or functional reasons. The balance cover hides the balance and also allows for the tilt and turn latch to glide without hitting the balance and causing an obstruction. Alternatively, the balances are painted, adding cost on the part.
The present invention addresses a previously unappreciated need for a balance that (a) will have an aesthetically pleasing body, (b) does not corrode, (c) is lighter and more cost effective (material cost) than current materials used, and/or (d) is easier to assemble and therefore less costly to assemble. Furthermore, the present invention is intended to. reduce the manufacturing complexity of a balance by, for example, incorporating a design wherein the threading of the pulleys with string can be out-sourced to lower-cost companies or countries, and thereby reducing the labor cost of threading. In addition, an aspect of the present invention enables a single balance to be used for a plurality of window sash heights, thereby reducing the number of balances that must be stocked in inventory by the window manufacturers who construct and install windows.
It is, therefore, and object of the present invention to provide a counter balance with a channel that is non corroding, semi rigid and is not required to carry a compressive load or stress as found in prior art counter balance designs.
It is another object of the present invention to make, full-length, rigid channel unnecessary while providing equivalent functionality of traditional counter balances using block and tackle assembly.
It is yet another object of the present invention to provide a balance design that incorporates, or allows the incorporation of, a balance cover.
It is yet another object of the present invention to provide a balance design that incorporates, or allows the incorporation of, a second, parallel balance into one assembly so as to carry a heavier sash. Such a design also reduces the material and labor costs associated with the fabrication and installation of the balances and covers.
It is another object of this invention to make the assembly of the balance rivet-free to allow for high-speed assembly with minimal labor.
It is another object of this invention to make the pulley assembly modular, and thereby enabling the threading of the pulley with the cord to be done separately from the assembly of the balance, and reducing labor costs.
It is another object of this invention to use the complete working range of the spring. and allow a single balance to be used for a plurality of sash heightsxe2x80x94thereby reducing the number of balance models needed to be maintained in inventory for a window manufacturer to make a complete set that can carry all the sizes and weights of window sashes required.
In accordance with the present invention, there is provided a balance assembly for providing vertical support to a window sash, comprising: a channel; a top shoe for insertion into one end of the semi-rigid channel; a bottom shoe for insertion into another end of the semi-rigid channel; a spring connected to a bottom end of the top shoe; and a block and tackle pulley assembly connected between a bottom end of the spring and the bottom shoe, wherein a cord from the pulley assembly extends outward from the bottom shoe for connection to the window sash.
In accordance with another aspect of the present invention, there is provided a balance assembly for providing vertical support to a window sash, comprising: a top shoe; a bottom shoe; a spring connected to a bottom end of the top shoe; a block and tackle pulley assembly connected between a bottom end of the spring and the bottom shoe, wherein a cord from the pulley assembly extends outward from the bottom shoe for connection to the window sash; and a balance cover, removably attached to said top and bottom shoes to provide a cover for the spring and pulley assembly.
In accordance with yet another aspect of the present invention, there is provided a method for installing a balance assembly on a window frame or a jamb liner to provide vertical support to a window sash, comprising: connecting, in series, a top shoe, a spring connected to a bottom end of the top shoe, a block and tackle pulley assembly connected to a bottom end of the spring, and a bottom shoe that retains a bottom pulley of the block and tackle pulley assembly, wherein a cord from the pulley assembly extends downward from the bottom shoe for connection to the window sash; affixing the top shoe to the window frame; affixing the bottom shoe to the window frame at a position below the top""shoe, wherein the spring is placed in tension; and placing a cover over the balance assembly, wherein the cover is attached to the top and bottom shoes.
The present invention. provides a simple construction, assembly. and installation method that addresses all the aforementioned problems that are inherent in the prior art block and tackle counter balance. In particular the U-shape channel is changed from a rigid metal part to a semi-rigid vinyl channel that is easily extruded and costs a fraction of the metal channel. An extruded vinyl part produced in accordance with an aspect of the present invention has the advantage of being less expensive, corrosion resistant and esthetically pleasing as it can be extruded in various colors to match any wood, metal or vinyl profile. Further a simple addition of an extension on the top of the U-channel allows it to simulate the balance cover. This integration of the balance and the balance cover allows a single piece to be installed at a lower cost to the window manufacturer.
The invention described herein is advantageous because it is efficient and inexpensive compared to other approaches for the construction of window sash balances. The improved design makes it unnecessary to have a single balance for each of a plurality of window sash heights. In addition, it allows the pre-assembly of a portion of the balance (pulley and cord) so as to reduce the complexity of the final assembly process. The techniques of the invention are advantageous because they provide a range of alternative balance sizes constructed in a similar fashion, each of which is useful in appropriate situations. As a result of the invention, the cost to manufacture and install window sash balances will be reduced from conventional balance designs.